As is well known in the art, semiconductor chips, such as computer chips, are manufactured such that they include a substrate, typically a silicon wafer. It is often desired during the manufacturing process of silicon wafers to determine a location on the wafer for various purposes, such as quality control and subsequent cutting of the wafer into individual chips.
Silicon wafers, such as the ones manufactured by Intel Inc. or by International Business Machines (IBM) both of the USA, typically include discrete geometrical features and markings thereon, as shown in FIG. 1 to which reference is now made. FIG. 1 illustrates a silicon wafer, generally referenced 10, which is generally circular but includes a flat edge 11 or a notch (not shown) in one side thereof.
Prior art methods for determining the orientation of a silicon wafer typically include the step of detecting, by employing a sensor, the limits of the flat 11 or of the notch of the silicon wafer while the wafer rotates on a stage. These methods are both time consuming and require that the circumference of the wafer, or at least the side of the flat or the notch facing the sensor, will be unobscured. Furthermore, they are not applicable when the stage cannot be rotated.